Looking at "chauraha" (crossroads), Simran thinks "chau" (four) here is just a quality-word…

Why

Simran is reasonably reaching for the कर्मधारय pattern again since a describing word ('चौ') sits before a noun ('राहा'), similar in shape to 'नीलकमल'. But when the first part is a NUMBER and the whole compound names a GROUP or collection of that many things, it is a distinct type — द्विगु समास (dwigu samas). 'चौराहा' doesn't mean 'a four-ish road' the way 'नीलकमल' means 'a blue lotus'; it means 'चार राहों का समूह' (a group/junction of four roads) — the numeral counts a collection, it doesn't describe one thing's quality. Test it: 'नीलकमल' can be paraphrased as 'नीला कमल' (one lotus, described as blue); 'चौराहा' cannot be paraphrased as 'चौ राहा' (one path, described as 'four-ish') — it only makes sense as a group of several paths meeting. Her brother is right: 'चौराहा' means 'a group of four roads' — this is द्विगु समास, where a numeral names a collection, not a quality.